The present invention relates to beds and, in particular, to a patient support system for hospital patients and other bed-ridden patients.
It has long been experienced that persons confined to a bed for prolonged periods tend to become inflicted with decubitus, also referred to as bedsores. These sores, which can have serious implications, result from a combination of conditions. In that regard, a hospital mattress is typically covered by a relatively unyielding surface, such as a thin, tight skin of washable, non-porous vinyl. A human body lying supine on such a surface is supported mainly at four locations, viz., the head, shoulder blades, tailbone, and heels. That is, the supportive forces of the support surface reacting against the body are concentrated in those regions. The resulting high pressures imparted against blood vessels in those regions can cause a disruption in the blood flow and an accelerated death of skin cells normally fed by those vessels. Furthermore, those parts of the body are typically in contact with moisture, such as urine and sweat, the latter being induced by heat which is retained by the non-porous vinyl skin. This moisture further weakens the dead skin and also harbors bacteria. When the dead skin ruptures, as from internal blistering or rubbing movements of the patient against the mattress, the bacteria is able to enter the ruptured skin and cause infections.
It is possible to retard or prevent the formation of decubitus by physically turning the patient on a periodic basis in order to re-establish blood circulation through blood vessels. However, not all hospitals are staffed sufficiently to carry out such a practice in a reliably effective manner. Control over the other sore-contributing factors (e.g., wetness and rubbing) is also difficult to achieve.
It has been recognized that the occurrence of decubitus can be prevented or retarded by reducing the pressure concentrations acting against the body so that the blood vessels are not restricted. Thus, if the supportive forces acting against the body are distributed more evenly, the pressures imposed upon the blood vessels can be reduced to levels below the internal pressures of the vessels, i.e., 30 mm of mercury. At least one effort to achieve such a force distribution, i.e., the so-called Clinitron bed, has achieved success. In such a bed, the patient lies upon a trough of sand which is covered by a rubber sheet. Air is pumped into the trough from below to elevate the sand upwardly against and in conformance with the patient's back so as to minimize the formation of pressure concentrations. Although successful, such beds are highly expensive, and thus have been of restricted usage.
Other proposals for redistributing the patient's weight have included a patient support system comprising a series of fulcrumed levers which act against the patient on opposite sides of their fulcrums. Thus, one end of each lever is acted upon by the downward forces of a relatively heavy portion of the patient's body, whereupon those forces are transmitted as upward forces by the opposite end of the lever. The upward forces act against a lighter portion of the patient's body. Consequently, the weight of the patient is distributed more evenly along the support surface. Arrangements of this type are disclosed, for example, in German Pat. No. 1,259,067 granted Jan. 18, 1968 and in Lippert U.S. Pat. Nos. 3,790,150 and 4,033,567 granted Feb. 5, 1974 and July 5, 1977, respectively.
In FIGS. 1 and 2 of the afore-mentioned German patent, there is disclosed an inclined reclining surface in which the levers are positioned on opposite sides of the bed frame. The levers are arranged as sets of lever assemblies, the assemblies being spaced in the longitudinal direction of the reclining surface. Each lever assembly comprises a series of transverse support rods carried by a pair of transversely spaced lever modules, with the levers of one module being interconnected with the corresponding levers of the other module by transverse bars. Thus, the transverse support rods are constrained, as they move up and down, to remain oriented parallel to the axes of rotation of the various levers.
In the afore-mentioned U.S. Lippert patents, a lever system extends across the entire undersurface of the mattress. The patient support surface is defined by the ends of uppermost ones of the levers.
Such force distributing lever systems are, in theory, capable of more uniformly distributing the patient's weight and thus will reduce the occurrence of pressure concentrations which can close-off the blood vessels. Thus, the incidence of weakened skin areas and the need to repeatedly reposition the patient can be reduced.
However, the other factors contributing to decubitus remain, viz., bacteria-laden moisture conditions and rubbing of the patient's skin (e.g., during raising and lowering of a typical articulated mattress support). It would be desirable to further reduce the influence of these other factors, as well as optimize, to as great a practical extent, the weight distribution which is achieved.
It is, therefore, an object of the present invention to provide a novel bed which reduces the occurrence of decubitus.
A further object is to provide such a bed which avoids the creation of sufficient force concentrations on a patient's body which can disrupt the blood flow in an appreciable number of blood vessels.
A further object is to provide such a bed which isolates the patient from much of the usual moisture such as sweat and urin.
An additional object is to provide such a bed as an articulated-type bed which resists the occurrence of a rubbing action against the patient's body during swinging movements (adjustments) of the articulated mattress frame.
Another object is to provide such a bed which affords a greater degree of movement of the support elements as compared with, say, that of the afore-mentioned German patent.
A further object is to provide such a bed which provides an unoccupied zone beneath the support elements which are capable of receiving various services and/or of conducting an air flow to the patient.